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  <div class="section" id="module-pty">
<h1>36.9. <tt class="xref docutils literal"><span class="pre">pty</span></tt> &#8212; Pseudo-terminal utilities<a class="headerlink" href="#module-pty" title="Permalink to this headline">¶</a></h1>
<p><em>Platforms: </em>IRIX, Linux</p>
<p>The <tt class="xref docutils literal"><span class="pre">pty</span></tt> module defines operations for handling the pseudo-terminal
concept: starting another process and being able to write to and read from its
controlling terminal programmatically.</p>
<p>Because pseudo-terminal handling is highly platform dependant, there is code to
do it only for SGI and Linux. (The Linux code is supposed to work on other
platforms, but hasn&#8217;t been tested yet.)</p>
<p>The <tt class="xref docutils literal"><span class="pre">pty</span></tt> module defines the following functions:</p>
<dl class="function">
<dt id="pty.fork">
<tt class="descclassname">pty.</tt><tt class="descname">fork</tt><big>(</big><big>)</big><a class="headerlink" href="#pty.fork" title="Permalink to this definition">¶</a></dt>
<dd>Fork. Connect the child&#8217;s controlling terminal to a pseudo-terminal. Return
value is <tt class="docutils literal"><span class="pre">(pid,</span> <span class="pre">fd)</span></tt>. Note that the child  gets <em>pid</em> 0, and the <em>fd</em> is
<em>invalid</em>. The parent&#8217;s return value is the <em>pid</em> of the child, and <em>fd</em> is a
file descriptor connected to the child&#8217;s controlling terminal (and also to the
child&#8217;s standard input and output).</dd></dl>

<dl class="function">
<dt id="pty.openpty">
<tt class="descclassname">pty.</tt><tt class="descname">openpty</tt><big>(</big><big>)</big><a class="headerlink" href="#pty.openpty" title="Permalink to this definition">¶</a></dt>
<dd>Open a new pseudo-terminal pair, using <a title="os.openpty" class="reference external" href="os.html#os.openpty"><tt class="xref docutils literal"><span class="pre">os.openpty()</span></tt></a> if possible, or
emulation code for SGI and generic Unix systems. Return a pair of file
descriptors <tt class="docutils literal"><span class="pre">(master,</span> <span class="pre">slave)</span></tt>, for the master and the slave end, respectively.</dd></dl>

<dl class="function">
<dt id="pty.spawn">
<tt class="descclassname">pty.</tt><tt class="descname">spawn</tt><big>(</big><em>argv</em><span class="optional">[</span>, <em>master_read</em><span class="optional">[</span>, <em>stdin_read</em><span class="optional">]</span><span class="optional">]</span><big>)</big><a class="headerlink" href="#pty.spawn" title="Permalink to this definition">¶</a></dt>
<dd><p>Spawn a process, and connect its controlling terminal with the current
process&#8217;s standard io. This is often used to baffle programs which insist on
reading from the controlling terminal.</p>
<p>The functions <em>master_read</em> and <em>stdin_read</em> should be functions which read from
a file descriptor. The defaults try to read 1024 bytes each time they are
called.</p>
</dd></dl>

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